Tomlinson-Harashima Precoding (THP) of static Pulse-Amplitude Modulation (PAM) is a known method to reduce receiver complexity, to allow spectral shaping in the transmitter to reduce alien cross-talk coupling, and to eliminate Decision Feedback Equalizer (DFE) error propagation even with large DFE coefficients. For example, 10GBASE-T, or IEEE 802.3an-2006, is a standard released in 2006 to provide 10 Gbit/s connections over unshielded or shielded twisted pair cables, over distances of up to 100 meters. The 802.3an standard specifies the wire-level modulation for 10GBASE-T to be Tomlinson-Harashima precoding (THP) pulse-amplitude modulation with 16 discrete levels (PAM-16) of {−15, −13, −11, −9, −7, −5, −3, −1, 1, 3, 5, 7, 9, 11, 13, 15}, encoded in a two-dimensional checkerboard pattern known as DSQ128 sent on the line at 400M symbols/sec.
Dynamic Modulation Coding (DMC) using overlapping subsets is a known method to achieve variable bit rates and different level of error resistance. For example, HDBaseT® Specification version 1 uses overlapping subsets of PAM-16 {−15, −13, −11, −9, −7, −5, −3, −1, 1, 3, 5, 7, 9, 11, 13, 15}, PAM-8 {−15, −11, −7, −3, 3, 7, 11, 15}, PAM-4 {−15, −7, 7, 15}, and PAM-2 {−7, 7}.